The field to which this invention pertains is curable compositions based on mixtures of epoxy-amine adducts and epoxy resins, particularly aqueous compositions wherein the epoxy resin is microemulsified in an aqueous solution of an acid salt of the epoxy-amine adduct.
Coating compositions based on organic solvent solutions of polyepoxide resins have been used successfully for a number of years. Such compositions have been particularly useful for coating the interior and exterior of food and beverage containers.
Due to increasing problems with air pollution, considerable efforts are being expended to convert organic solvent containing coating compositions to water based systems, i.e., coating systems based on solutions, dispersions and emulsions of film forming resins in water. One of the problems in the use of such aqueous systems is the inability of the resin to properly wet the substrate and to form a continuous coating. Another problem is the poor resistance properties, e.g., hot water resistance, of the cured coatings. Still other problems are the mechanical stability, e.g., particle settling, freeze-thaw stability and shear sensitivity, and chemical stability, e.g., pot-life, of aqueous coating systems.
Due to present and potential world-wide energy shortages, considerable effort is being expended to develop coating compositions which can be baked and cured rapidly at low temperatures, e.g., at 200.degree. to 300.degree. F.
It is therefore an object of the present invention to provide a two component aqueous based coating system wherein when the components are mixed forms a curable coating composition having improved mechanical and chemical stability and which when applied as a film exhibits improved particle coalescence, film continuity, adhesion, flexibility, chip resistance and the like.
It is a further object of the present invention to provide a coating composition capable of being cured with low energy input, i.e., a coating composition which can be cured at low temperatures in a relatively short time.
A still further object of the present invention is to provide a process for preparing the curable coating composition.
These and other objects and features of the invention will become apparent from the claims and from the following description.